Sometimes a shop may have AMP installed on one shop, and migrate their store to a new URL, and then install AMP on the second shop. This will help answer all of your questions.
How can I migrate AMP from one shop to another?
In general, the process is simple. Simply install AMP on the new shop, and set up your AMP pages, and publish them. If you need our team to migrate theme settings (meaning any edits you made within the AMP theme customizer) from one shop to another, reach out to our support team and we'll be happy to help you.
Do I need to create redirects from Shop A to Shop B for AMP?
Generally, no. When Google crawls Shop A, they index AMP pages on Shop A. When Shop A is removed from the Google index, then Shop A's AMP pages are removed from the Google index as well. When Shop B gets indexed, if you have AMP activated on Shop B, then the AMP pages will be indexed on Shop B.
Will old AMP links automatically redirect from Shop A to Shop B?
No, there is not a feature to make this happen. The only way to make this happen would be to redirect your pages at the DNS layer, using your DNS provider. While we don't have a tutorial on this, we recommend reaching out to your DNS provider and asking them how to create redirects from one domain to another.
Will my new AMP pages be indexed on Google?
Yes, just make sure you publish your AMP pages on your new shop (Shop B, in this example).
Will my old pages be de-indexed on Google?
Yes, once Google realizes you no longer have Shop A active, then they will de-index Shop A's AMP pages
Do I need to submit a sitemap?
No, Google doesn't recommend submitting a sitemap for AMP pages. Google indexed AMP pages by first crawling your non-AMP pages, so your original sitemap (automatically submitted by Shopify) works just fine. There is no need to submit a sitemap.
Do I need to unpublish the pages from my first shop?
We recommend doing this once you have completely switched to the second shop (Shop B). Once Google crawls Shop A and notices that these pages aren't available anymore, then they will remove Shop A's AMP pages as well.
What happens if I remove AMP from a shop?
If you remove AMP, then the AMP pages will no longer work. The app requires an installation in order to have the AMP pages work on your shop.